FIGS. 13A and 13B are diagrams showing a general substrate package structure of this type. Specifically, FIG. 13A is a cross-sectional view showing a state before two substrates 100 and 200 are connected to each other, and FIG. 13B is a cross-sectional view showing a state where the two substrates 100 and 200 are connected to each other, that is, a substrate packaged state.
As shown in FIG. 13A, the first substrate 100 at the lower side and the second substrate 200 at the upper side are disposed so as to confront each other at one surface sides thereof. Furthermore, a bump 10, 20 formed of gold or the like by a ball bonding method is provided on one surface of each of the first and second substrates 100 and 200.
In order to package both the substrates 100 and 200, the bump 10 at the first substrate 100 side and the bump 20 at the second substrate 200 side are positioned to each other while the one surface of the first substrate 100 and the one surface of the second substrate 200 are confronted to each other as shown in FIG. 13A, and then both the bumps 10 and 20 are press-fitted to each other as shown in FIG. 13B, whereby both the bumps 10 and 20 are connected to each other and the substrate package structure is formed.
Here, the bumps 10 and 20 of the substrates 100 and 200 are designed so that the widths A of the tip portions thereof are substantially equal to each other.
Therefore, a permissible value W1 for the positioning error of both the bumps 10 and 20 which is caused by a positional displacement of both the substrates 100 and 200 in the plane direction, in consideration of securing joining quality between the bumps 10 and 20, is equal to or less than a half (½) of the width A of the tip portion, that is, a value of A/2 or less. This is a narrow value.
When the permissible value W1 for the positioning error is narrow as described above, it is needed to carry out high-precision positioning while checking the bump connection portion by a visualizing device or the like, and the labor and cost needed for the positioning of both the substrates 100 and 200 are increased.
Therefore, there has been hitherto proposed a method for providing a wall to an electrode at the substrate side by plating or resist and carrying out the positioning through the wall (see JP-A-2002-261116). Furthermore, there have been also proposed a structure that a wall or dam is provided so as to prevent flow of resin to a portion of an element which is sensitive to stress applied when final resin sealing is carried out although it does not aim at the positioning (see JP-A-9-232366, JP-A-6-204293).
However, the positioning method disclosed in JP-A-2002-261116 is based on the assumption that the electrode is formed by plating and thus the cost is increased. Furthermore, the wall merely serves as a mark or guide, and it is designed under the restricted condition of the dimension of the electrode, and thus it does not contribute to facilitation of the positioning.
On the other hand, the wall or dam disclosed in JP-A-9-232366 or JP-A-6-204293 does not contribute to the positioning of the substrate, and has no object to facilitate the positioning in the substrate packaging work.